A single-wafer type spin cleaning apparatus cleaning a substrate to be processed, for example, a semiconductor wafer (“a wafer”) removes dusts or native oxides on a wafer surface by rotating the wafer while supplying, for example, alkaline or acid chemical liquids to the wafer surface. The chemical liquid remaining on the wafer surface is removed by a rinsing process using, for example, deionized water (DIW), and subsequently, spin-drying for throwing off the remaining liquid by rotating the wafer is performed.
However, as the semiconductor devices are highly integrated, a problem of a so-called pattern collapse has increased in processing of removing, for example, the liquid. The pattern collapse is a phenomenon in which, when drying the remaining liquid on the wafer surface, the remaining liquid is unevenly dried at the left and right sides of, for example, a convex portion of concavo-convex portions forming a pattern so that the balance of the surface tension horizontally pulling the convex portion is lost, and as a result, the convex portion falls down in a direction in which more liquid remains.
As a technique of removing the liquid remaining on the water surface while preventing the occurrence of the pattern collapse, a drying method using a fluid in a supercritical state (a supercritical fluid) which is a kind of high-pressure fluid is known. The supercritical fluid has lower viscosity as compared to a liquid, and also has superior liquid dissolving capability. Further, there is no interface between the supercritical fluid and a liquid or a gas which is in an equilibrium state. Therefore, when the wafer having the liquid adhered thereon is substituted with the supercritical fluid, and thereafter the supercritical fluid is changed to a gaseous state, the liquid may be dried without being influenced by the surface tension.
However, in the case of performing the drying process, the pressure in a processing container is boosted to, for example, about 10 MPa. For this reason, a sealing structure that airtightly closes a wafer carrying port formed in a processing container by a cover is required to maintain airtightness even when the pressure in the processing container is changed and to further prevent the generation of particles.
Japanese Patent Application Laid-Open No. 10-47483 (FIG. 2 and paragraphs 0016 and 0017) suggests a technology that, in a sealing structure for sealing the inside of a can body by fastening a body flange and a lid flange with a clamp ring, a concave portion formed on the body flange and a convex projected portion formed on the lid flange interlock, and a packing of the convex projected portion contacts the concave portion to seal the inside of the can body. However, since the configuration of Japanese Patent Application Laid-Open No. 10-47483 has the sealing structure fastening the shell flange and the lid flange with the clamp ring, the sealing structure may not be applied to a configuration that airtightly closes a carrying port and a cover of a processing container as it is, and the problems of the present disclosure cannot be solved even by the configuration of Japanese Patent Application Laid-Open No. 10-47483.